Self-propelled vehicles are well known in the art and take many different forms. One of the more prevalent is the tricycle commonly used by children which is a three wheeled vehicle supporting a frame, the front wheel having a pair of handlebars and being steerable, and a pair of pedals for foot operation associated with a drive mechanism to propel a drive axle at the rear of the vehicle. The child usually sits on a seat positioned near the rear of the vehicle which is conveniently spaced from the pedals such that it is comfortable.
The drive mechanisms for tricycles have taken many forms in the prior art. Perhaps the simplest version is the crank where crank arms are mounted to the front wheel with pedals attached at their outer ends such that the child's legs and feet turn the cranks to thereby rotate the forward wheel and propel the vehicle. Still other more complex drive mechanisms include pedals associated with a gear or chain drive mounted at the back for driving the axle to which are mounted a pair of rear wheels. In some prior art tricycles, a mechanism is even provided for shifting of the relative position of the gears to thereby change the direction of vehicle movement as the pedals are reciprocated.
In all of these prior art vehicles, except for the simple crank handle design, the drive mechanisms are quite complex utilizing expensive gears or drive chains which also are susceptible to breakage or misalignment through the rough-house type of usage generally experienced by a child's toy. As can be appreciated, the complexity of the design can contribute to the limited availability and salability of a child's toy such that simplicity of design and operation is desirable for many reasons.
In order to solve these and other problems in the prior art, the inventors herein have succeeded in designing and developing a drive mechanism for a child's vehicle, such as a tricycle, which utilizes a simplistic but elegant cam and cam follower drive mechanism which is pedal operated and which also has a shifting mechanism for changing the vehicle's direction of movement from forward to reverse, and vice-versa. In essence, each pedal has an associated cam follower mounted thereon, with the cam follower being urged against its associated cam by a spring or the like. Each cam is mounted to a drive axle such that as the cam follower moves along the cam, it rotates the cam to thereby rotate the drive axle and drive wheel, thereby propelling the vehicle. Each cam has a unique shape which approximates an airplane propeller, or pair of flower petals, generally including a pair of lobes which are 180.degree. offset. Additionally, the cams are themselves 90.degree. offset. With these offsets, the pedals move alternately up and down to accommodate a reciprocal pumping action commonly used in vehicles, such as a tricycle. At the same time, with this arrangement the direction of vehicle movement can be changed by shifting the pedals and cam followers either forwardly or rearwardly to thereby change their relative position with respect to the cams such that the rollers move along the cams in the opposite direction to thereby rotate the drive axle in the opposite direction causing the vehicle to move in the opposite direction.
As can be appreciated, this drive mechanism is elegantly simple, inexpensive to manufacture, relatively insensitive to rough-house handling and treatment, includes no gears or chains which may be jammed or moved out of alignment, requires little or no lubrication or maintenance, and contributes to a versatile design providing both forward and rearward movement.
In addition to the forward and rearward directions of movement, there is a third universal position intermediate the other two positions in which the direction of rotation may be changed by merely stopping the pedaling action in a central or neutral pedal position, and then restarting in the opposite direction to thereby change the direction of rotation of the cams and the direction of movement of the vehicle. Thus, changing from forward to rearward movement requires only an intermittent hesitation of pedal movement and then a restarting of pedal movement with the opposite foot. Thus, the child has the opportunity to change direction of movement in a relatively easy and quick manner.
In an alternate embodiment, the drive mechanism may be mounted to the front wheel of the vehicle in a manner more akin to the conventional tricycle of the prior art which utilizes crank handles on the front wheel. This alternate embodiment may perhaps be even less expensive than the first embodiment to manufacture and hence may be more desirable from a cost standpoint. Furthermore, its compact design may be more suitable for smaller sizes while the first embodiment may be more suitable for larger sizes of vehicles.
While the principal advantages and features of the invention have been discussed above, a greater understanding of the invention and appreciation for its features may be attained by referring to the drawings and description of the preferred embodiment which follow.